What form do I use to ask the probate court to remove an executor of a Will?

Assuming the maker of the will is deceased, then a petition for probate would be filed and you can at that time object to the executor named in the will by filing an objection. If the person who drafted the will has named a executor you do not like, too bad, as the power to change designated executors is with the maker of the will by amendment or revocation of the will and drafting of a new will.

If you are talking about removing a personal representative who has already been appointed by the court, you can petition the court to do so if the executor/personal representative is not complying with the will or breaching his/her fiduciary duty. 

You should retain an attorney to file the petition because it is very difficult to remove an executor, especially if the testator has given the executor broad powers.  Therefore, in that respect, I disagree with Attorney Waid.